The disclosure of Japanese Patent Applications No. 2002-166917 filed on Jun. 7, 2002, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to an intake device for an internal combustion engine of a motor vehicle or the like.
2. Description of the Related Art
An example of the internal combustion engine-purposed intake devices that prevent release of unburned gasses, such as fuel vapor and the like, is an intake device as shown in FIG. 6 in which an adsorbent layer 101 is formed around an outer peripheral surface of an intake passageway 100 (Japanese Patent Application Laid-open No. 2002-4956). In this intake device for an internal combustion engine, unburned gas flowing in the intake passageway 100 is adsorbed and trapped by the adsorbent layer 101. Therefore, in the internal combustion engine-purposed intake device, it is essential that the adsorbent layer 101 be formed on an outer peripheral surface of the intake passageway 100. However, due to the provision of the adsorbent layer 101, the number of component parts of the intake device increases and the production process of the device becomes rather complicated, in comparison with a conventional internal combustion engine-purposed intake device.
Accordingly, it is an object of the invention to provide an internal combustion engine-purposed intake device that is made capable of preventing release of unburned gas into the atmosphere by performing a simple process on a conventional structure.
In accordance with the invention, an intake device for an internal combustion engine includes: a first intake pipe which is connected to the internal combustion engine so as to conduct an intake air to the internal combustion engine, and which has an opening portion that is provided in an upstream-side lower portion of the first intake pipe located at an upstream side in a flowing direction of the intake air; and a second intake pipe which has a downstream-side end portion that faces an upstream-side end portion of the first intake pipe, with a gap formed between the downstream-side end portion of the second intake pipe and the upstream-side end portion of the first intake pipe, and which conducts the intake air to the first intake pipe. An unburned gas reflux passage is provided which conducts an unburned gas from the internal combustion engine to the first intake pipe. The intake device further includes a container that surrounds the gap and the opening, and that receives the unburned gas flowing from the opening portion.
According to the above-described internal combustion engine-purposed intake device, intake air is conducted to the internal combustion engine via the second intake pipe and then the first intake pipe. The unburned gas from the engine is conducted to the first intake pipe via the unburned gas reflux passage. Since the unburned gas has a greater specific gravity than air, the unburned gas, during a stop of the engine, moves along a lower portion of the first intake pipe, and then falls into the container via the opening portion, and thus resides in the container. In the invention, the unburned gas refers to a gas that has not been completely burned, and includes an incompletely burned gas as well as a gas that has not been burned at all. The unburned gas also includes a fuel vapor that flows back through the first intake pipe due to diffusion from the internal combustion engine during a stop of the engine, as well as a gas conducted to the first intake pipe via the unburned gas reflux passage as described above.
Due to the provision of the opening portion in the upstream-side lower portion of the first intake pipe and the formation of the container surrounding the gap and the opening portion, unburned gas can be stored in the container. Therefore, it becomes possible to prevent release of unburned gas into the atmosphere. The opening portion is provided in a lower portion of an upstream-side portion of the first intake pipe. The xe2x80x9clower portionxe2x80x9d herein includes a lowermost end portion of an intake pipe whose axis extends substantially horizontally, and also includes a portion of a lower half portion of an intake pipe that is other than a lowermost end portion. During an operation of the internal combustion engine, unburned gas is refluxed to the first intake pipe and is then conducted to the engine by a suction stream of atmospheric air. Furthermore, suction noises enter the container via the gap between the first intake pipe and the second intake pipe. Therefore, the function of the container as a resonant chamber is maintained. If the first intake pipe and the second intake pipe that face each other are joined at a portion, the above-stated operation and advantages can be achieved as long as a gap is formed between the two pipes.